Healthy Ecosystems

Most waters in the Lake Champlain Basin are free of aquatic invasive species and need protection; human behavior can cause the spread of invasive species.

Aquatic invasive species are plants, animals, and pathogens that are non-native to the watershed and have been proven to cause harm to the economy, environment, or human health. Invasive species can divert food resources from native species, reduce light penetration, change habitats, impair water quality, interfere with recreational opportunities, and reduce property values. Invasive pathogens also threaten the health of native fish and sport fisheries.

Most introduced non-native species do not become established populations in the ecosystem. Those that do establish can cause serious widespread impacts that require significant resources to manage. Just over a dozen established aquatic non-native species are considered invasive in Lake Champlain, including the zebra mussel, water chestnut, Eurasian watermilfoil, phragmites, alewife, and spiny and fishhook waterflea (Figure 15). Inventories completed by state programs and community monitor groups supported by the Adirondack Park Invasive Plant Program and volunteers in the Vermont Invasive Patroller Program indicate that 75% of lakes in the Adirondacks and 80% of the lakes in Vermont are free of aquatic invasive species. The primary source of new aquatic invasive species to our region is ballast water taken in by ships at their freshwater ports of origin around the world and then released into the Great Lakes. Once these invasive species are established in the Great Lakes, the primary pathway for their introduction into Lake Champlain is through canals that connect the Great Lakes, St. Lawrence River, and Hudson River to Lake Champlain (Figure 16).

The fishhook waterflea invaded Lake Champlain in 2018 and has changed the base of the food web.

The fishhook waterflea is the 51st aquatic non-native species to be detected in Lake Champlain and poses a significant risk of spread to other waterbodies in the region. Like the invasive spiny waterflea (detected in Lake Champlain in 2014), this crustacean is a voracious predator. It has impacted the Lake’s phytoplankton community and now is outcompeting the spiny waterflea. Its small size and resting egg life stage can hitchhike unnoticed in bilge, motor, or bait bucket water. However, when thousands of the species’ barbed tails get hooked onto and foul fishing line and gear, they are hard to miss. The fishhook waterflea is native to northern Europe and Asia. The species was likely introduced with released ballast water into the Great Lakes and then spread overland on boats, trailers, and other recreational and fishing equipment to Lake Champlain. Over the past three years, boat launch stewards helped to remove and decontaminate fouled gear and flush out boat motors and compartments from watercraft exiting Lake Champlain during the species’ population peak in late June through early July.

Invasive species are impacting Lake Champlain’s fishery.

Non-native and invasive species continue to challenge Lake Champlain, and it is difficult to quantify their impacts. When a population increases, it pressures other species that compete for similar food and habitat. Zebra mussels have colonized most of the Lake and filter untold amounts of plankton each day, reducing food availability. Alewife continue to outcompete native smelt, thus changing the food web, and are now the primary source of food for Atlantic salmon and lake trout. Alewives are rich in thiaminase, an enzyme that destroys thiamine in the fish that eat them, leading to early mortality syndrome in newly hatched fish or immune dysfunction. Hatchery-reared eggs are now bathed in thiamine to address thiaminase deficiency and improve survival.

Sea lamprey wounding rates on lake trout and Atlantic salmon are varied.

Sea lamprey are a parasitic eel-like fish that feed on Atlantic salmon, lake trout, and other sport fish in Lake Champlain. They spend the first four years of their lives as larvae in the Lake’s rivers and then transition to the Lake and survive by attaching to fish to feed on their body fluids. Sea lamprey wounding rates on lake trout and Atlantic salmon have varied over the past three years. Wounding rates on lake trout are well above the target wounding rate of 25 wounds per 100 fish, but wounding on Atlantic salmon is hovering just above the goal of 15 wounds per 100 fish (Figure 17). Sea lamprey wounding rates have historically been used as an indicator of the impact of sea lamprey on the health of fish populations, though these rates are not a direct, accurate measure of the size of the sea lamprey population. Primary methods for sea lamprey management include application of pesticides to most sea lamprey-bearing tributaries every four years and barrier installation to prevent spawning in tributaries. Nontarget impacts of pesticides on rare species are a concern in several tributaries.

Some new aquatic invasive species are getting closer to the Basin.

The invasive aquatic plant hydrilla, round goby, and quagga mussels all are approaching Lake Champlain and are considered to be major threats here. Hydrilla is an aggressive aquatic plant that could overwhelm shallow areas of the Lake; it requires years of herbicide treatment to manage. Hydrilla plant fragments were intercepted by a Lake Champlain boat launch steward in 2019 on a jet ski coming from the Connecticut River. Round goby fish are aggressive egg predators that outcompete native benthic fish like slimy sculpin. Round gobies can bioaccumulate toxic substances, such as PCBs, from eating zebra mussels, making them a threat to their predators. Gobies have been linked to bird deaths in the Great Lakes. They are present in the St. Lawrence and Richelieu Rivers to the north and have been recently detected moving farther east in the Erie Canal toward the Hudson River by the U.S. Geological Survey. Quagga mussels are similar to the zebra mussel that invaded in 1993, but they would have a greater impact if introduced to Lake Champlain. Quagga mussels can grow in deeper waters and have greater reproductive advantages than zebra mussels. Their arrival would put many historic shipwrecks at risk, and their filter feeding would have significant impacts on plankton at the base of the Lake Champlain food web. Quagga mussels were intercepted on a watercraft that had previously visited Lake Ontario while it was attempting to launch into Lake Champlain in 2018.

Aquatic invasive species spread prevention efforts are focused on managing the pathways and human activities that may unintentionally aid their introduction.

Once introduced, aquatic invasive species are often impossible to eliminate and very costly to manage. Preventing the introduction of these species is key to maintaining the health of the Lake Champlain ecosystem. The Champlain Canal that connects the Lake Champlain and Hudson River basins is a pathway for aquatic invasive species introduction. The U.S. Army Corps of Engineers is leading a study to determine how to best prevent the transfer of aquatic invasive species between these two basins. Groups in New York also are examining the Erie Canal system as part of the governor’s Reimagine the Canals Initiative to identify opportunities to prevent the spread of aquatic invasive species, boost tourism, reduce flooding, enhance irrigation and recreational fishing, and restore wetlands. These efforts examine alternatives that would allow for recreational traffic to move through the system but would prevent fish, plants, plankton, mollusks, and viruses from swimming or floating from one watershed to another.

Boats, trailers, and recreational equipment also can carry invasive species to the Lake Champlain Basin. The LCBP and Adirondack Watershed Institute of Paul Smith’s College operate watercraft inspection and decontamination programs on Lake Champlain and across the region to prevent the spread of invasive species. Data from this program show that watercraft coming from high-risk waterbodies were most frequently from the Hudson River, St. Lawrence River, and Connecticut River, where there are more and different aquatic invasive species present that could be introduced to Lake Champlain (Figure 18). There are simple steps that residents in the watershed can take to prevent the spread of invasive species, such as planting native species; surrendering aquarium fish instead of releasing them into the water; following baitfish regulations; and cleaning, draining, and drying watercraft and recreational equipment after each use.

Coordinated and intensive annual water chestnut management efforts in Lake Champlain are slowly reducing the extent of this species.

The water chestnut is an invasive annual plant that forms dense leafy mats that float on the water surface. In the southern end of Lake Champlain, water chestnut limits boat traffic and recreational use, crowds out native species, and creates areas without oxygen that are uninhabitable to fish and other organisms. Isolated populations of water chestnut are found in other areas of the Lake. Lake Champlain’s water chestnut control program is a long-standing success story. U.S federal agencies, state and provincial bodies, and nongovernmental organizations provide support to harvest water chestnut mechanically and by hand in Lake Champlain and other inland waters in the Basin. While management from year to year may have varied results, efforts have pushed the dense (>25% cover) populations from Crown Point down to the Dresden Narrows over the past 20 years (Figure 19).